Engine oils are finished crankcase lubricants intended for use in automobile engines and diesel engines and generally consist of a lubricating base oil and additives. Lubricating base oil is the major constituent in these finished lubricants and contributes significantly to the properties of the engine oil. In general, a few lubricating base oils are used to manufacture a variety of engine oils by varying the mixtures of individual lubricating base oils and individual additives.
The dewaxing processes used to manufacture lubricating oil basestocks can result in breakdowns or inefficiencies in the processes affording a quantity of wax beyond an acceptable basestock manufacture specification. The presence of contamination wax or excessive wax content can occur as a result of leakage of wax through rips or tears in the wax filter cloth used in solvent dewaxing processes, overloading of the solvent dewaxing processes, basestock channeling through the catalytic beds used in catalytic dewaxing processes, over-loading of the catalytic dewaxing process, poor catalyst activity or selectivity or because the crude oil or feedstock to the process is significantly different than expected, resulting in unsuitable dewaxing process conditions.
Lubricating oil basestocks containing undesirable quantities of contamination wax or excessive wax can result in growth of wax crystals, which is typically a slow process. The growth may only become visible upon visual inspection after several days or weeks. As a consequence, when fully formulated oils are produced using basestocks containing unidentified undesirable wax contamination, an entire batch of product may fail to function properly at low temperature.
In particular, the formulated oil may exhibit unsatisfactory low temperature viscometric properties. Indeed, formulated lube oils have been found to fail key low temperature viscometric properties for the oil [e.g., the cold cranking simulator (CCS) viscosity or the mini-rotary viscometer (MRV)], despite passing the specification established for the oil with respect to cloud point and/or pour point.
Contamination wax or excessive wax can result in a highly non-Newtonian increase in low temperature viscometrics in fully formulated oils resulting in high viscosities and/or poor pumpability at low temperatures. With regard to engine oils, hydraulic oils or transmission fluids, the increase in low temperature viscometrics or the reduction in or loss of filterability results in a failure of the oil to properly lubricate key components. Moreover, wax crystals can form a haze in the oil upon standing, which is undesirable for customers from a cosmetic perspective, as well.
The Society of Automotive Engineers (SAE) J300 standards provide the minimum specifications for the various viscosity grades of engine oils in the United States. The SAE J300 standards include MRV viscosity specifications. Due to the problems associated with contamination wax or excessive wax, there is a need for engine oils meeting low temperature viscometric properties including MRV viscosity specifications under the SAE J300 standards.